Plasma membranes from cancer and normal cells are to be examined by electron diffraction under physiological conditions, using high voltage electron microscopes. Plasma membranes are to be isolated from human normal and leukemic lymphocytes, normal liver and hepatoma cells, human malignant and benign tumor cells and from cultured normal and transformed cells. The differences in cell surface structures as well as the phase state of the membrane phospholipids are to be studied. The temperature, hydration states and chemical treatments will be monitored. The differences in cell surface structures are to be correlated with the malignancy and other biological parameters of the cells.